Medical practitioners must from time to time measure the dorsiflexion of the human foot for medical purposes. Dorsiflexion is defined as the movement of the foot at the ankle upwardly toward the knee along the sagittal plane. In order to measure dorsiflexion, a more or less standard goniometer is used and may be similar to the goniometer shown in U.S. Pat. No. 3,270,420 which has substantially two flat members pivoted together and having a scale thereon for measuring the amount of pivoting of one with respect to the other.
To measure dorsiflexion with such a device, a reference line on one of the goniometer arms is aligned with the lateral midline of the lower leg using the head of the fibula as a reference point. The other arm of the goniometer is placed at 90.degree. with respect to the first arm and the axis of pivoting between the two arms is more or less aligned with the pivotal axis of the foot with respect to the leg. Then the foot is pivoted manually as much as is possible, and this angle of movement between the starting and finishing positions is measured and is considered to be the dorsiflexion. Normally, this assessment is done while the patient is sitting with the patient's feet off the ground.
A problem with conventional goniometer instrumentation for measuring dorsiflexion is that it does not allow the medical examiner to consider the manner in which the entire foot interacts with the ground while performing ankle dorsiflexion assessment.
Another problem associated with currently available instrumentation for the assessment of ankle dorsiflexion is that medical examiners use a variety of anatomical landmarks to determine how the two arms of the goniometer are aligned with the leg, foot and ankle. This results in a lack of consistency among professionals claiming to measure the same motion. The actual measurement as obtained with currently available instrumentation therefore becomes subjective because there is no common line used to represent the transverse plane. Furthermore, dorsiflexion assessment is awkward and cumbersome with the currently available instrumentation. Manipulation of the subtalar joint, which is important in proper dorsiflexion assessment, can distort the dorsiflexion measurement using currently available instrumentation.
Consequently, there is a need for a goniometer structure which will overcome the aforementioned problems and facilitate consistent, objective dorsiflexion assessment.